Method and machine for shaving a conical gear

ABSTRACT

A method of and machine for shaving a conical gear, such as for example, a conical spur gear or a conical helical gear, and using only a standard cylindrical shaving cutter. The invention includes arranging the axis of the conical gear at an angle to the axis of the cylindrical shaving cutter so that the pitch line of the gear adjacent the cutter is generally parallel to the pitch line of the cylindrical cutter during the shaving operation.

iJnited States atent [191 Marano June 19, 1973 METHOD AND MACHINE FOR SHAVING A CONICAL GEAR [75] Inventor: Louis G. Marano, Racine, Wis.

[73] Assignee: Twin Disc, Incorporated, Racine,

Wis.

[22] Filed: Feb. 2, 1972 [21] Appl. No.: 222,922

[52] US. Cl. 90/1.6, 90/9 [51] B23f 19/06 [58] Field of Search 90]].6, 7, 9

[56] References Cited UNITED STATES PATENTS R23,053 ll/l948 Mentley 90/l.6

Primary ExaminerFrancis S. Husar Attorney-James E. Nilles [57] ABSTRACT A method of and machine for shaving a conical gear, such as for example, a conical spur gear or a conical helical gear, and using only a standard cylindrical shaving cutter. The invention includes arranging the axis of the conical gear at an angle to the axis of the cylindrical shaving cutter so that the pitch line of the gear adjacent the cutter is generally parallel to the pitch line of the cylindricalcutter during the shaving operation.

7 Claims, 12 Drawing Figures Patented June 19, 1973 3,739,686

6 Sheets-Sheet 1 FIG. I

Patented June 19, 1973 3,739,686

. 6 Sheets-Sheet 2 FIG.2b

Patented June 19, 1973 3,739,686

6 Sheets-Sheet 5 FIG. 3a

Patented June 19, 1973 3,739,686

6 Sheets-Sheet 4 Patented June 19, 1973 6 Sheets-Sheet 5 Patented June 19, 1973 3,739,686

6 Sheets-Sheet 6 BACKGROUND OF THE INVENTION The invention pertains generally to metal working and more particularly to shaving conical gears after they have been roughed out by a hobbing process. In

gears of this type it is desirable to provide a straight or crowned tooth rather than a hollow ground tooth, to prevent end loading of the gear teeth that results in breakage.

Prior art gear shaving techniques utilize a conical shaving cutter made with a hollow lead to produce a straight or crowned conical gear, and in this prior method the cutter and gear axes were arranged in parallel planes during the gear shaving process. There were certain shortcomings in this prior method however, such as cost and time required for shaving cutter for this diagonal traverse shaving method, which utilized a cutter that was of an opposite form to that form desired to be produced on the gear. Furthermore, it was costly to re-sharpen such conventional diagonal traverse cutters. In addition, such prior art conical shaving cutters were single purpose tools and could be used only with any one single conical gear design. The prior art conical cutter has an inherent disadvantage in that, for any specific magnitude of crown which was built into it, it was usable only with a particular design of gear to be made by the cutter. Generally, it was extremely difficult, costly, and time consuming to manufacture conical gears by means of the prior art methods.

One example of the prior art is shown in the U.S. Pat. No. 2,464,963 which issued Mar. 22, 1949 to Bregi et a]. and entitled Gearing.

SUMMARY OF THE INVENTION The present invention provides a method and machine for shaving a frusto-conical gear, which is commonly referred to simply as a conical gear, with a standard, cylindrical shaving cutter. The present invention includes rotatably supporting the gear to be shaved with its axis positioned at an angle with respect to the axis of the cutter, that is the axes are located in nonparallel planes, and with the pitch line of the gear which is adjacent the cutter positioned in parallelism with the pitch line of the cylindrical cutter. The cutting pass is made between the gear and rotatably driven cutter in one axial direction and after that particular pass is made, the next cutting pass is made in the opposite I axial direction during which the gear and shaving cutter.

rotate in other directions. Furthermore, as the gear and cutter move axially relative to one another during a cutting pass, the angle of the gear is rocked in a plane containing the axis of the cutter to thereby effect a crowning of the tooth. 1

The invention provides for the use of a standard, cylindrical shaving cutter for shaving a conical gear and this is accomplished by positioning the axis of the conical gear at an angle to the axis of the cutter, in nonparallel planes, so that the pitch lines of the gear and cutter remain parallel during the shaving operation, except that while the cutting pass is being made, the conical gear is also rocked very slightly to produce a crowning of the gear tooth.

These and other objects and advantages of the present invention will appear hereinafter as this disclosure progresses, reference being bad to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective and generally schematic view showing the relationship between a conventional, noncylindrical, shaving cutter and a conical gear being shaved, in accordance with the prior art method of diagonal traverse shaving;

FIG. 2 is a perspective view of a conical gear tooth having a hollow lead, as made with certain other prior art methods, the tooth being shown partially in broken lines so as to also show a cross sectional view through the tooth;

FIG. 2a is a lead chart of the conical gear shown in FIG. 2 having a hollow lead;

FIG. 2b is a transverse, cross sectional view taken on line 212-212 of FIG. 2;

FIG. 3 is a perspective view of a conical tooth of the crowned type and as produced by means of the present invention, the tooth being shown partially in broken lines so as to also show a cross section through the tooth;

FIG. 3a is a lead chart of the tooth shown in FIG. 3;

FIG. 3b is a transverse cross sectional view taken along the line 3b-3b in FIG. 3;

FIG. 4 is a perspective, schematic view of a conventional cylindrical shaving cutter when commencing a shaving pass on a conical gear in accordance with the present invention, the conical gear being arranged with its axis at an angle to the axis of the shaving cutter so that the conical gear and cutter are in shaving mesh and furthermore, showing (by curvilinear arrow) the slight rocking of the gear at the commencement of the cutting pass so as to effect crowning of the gear;

FIG. 5 is a view similar to FIG. 4 but when the gear is halfway throughits cutting pass, no rocking of the gear occurring at this stage;

FIG. 6 is a view similar to FIGS. 4 and 5, but showing the gear at the end of the above cutting pass and just prior to the gear reversing its direction;

FIG. 7 is a view similar to FIG. 6 except that the rotation of the cutter and gear has been reversed as when the gear has commenced its cutting pass in the reverse direction to that shown in FIGS. 4 and 5; and

FIG. 8 is a view of a gear shaving machine and showing the support for rotatably journalling the gear with its axis at an angle to the axis of the cylindrical cutter so that the pitch line of the gear and cutter are in shaving mesh.

PRIOR ART EXAMPLE A method of shaving conical gears is shown in FIG. 1 and is commonly referred to as the diagonal traverse shaving method and utilizes a conventional, noncylindrical shaving cutter CC. This cutter CC is also referred to as a conical cutter and it is generally frustoconical but of opposite form to that form to be shaved on the conical gear CG. The axis AC of the cutter and the axis AG of the gear are located in parallel planes, and the gear CG is moved back and forth under the cutter along a diagonal, traverse line indicated by the arrow DT. The disadvantages of this prior art method have been described partially in the above Background of the Invention."

DESCRIPTION OF A PREFERRED EMBODIMENT The present invention provides a method and machine for making a conical gear having teeth of the straight or crowned type, and a tooth of the crowned type made with the present invention is shown in FIG. 3. This type of tooth is desirable to eliminate end load on the tooth with its consequent breakage. It will be noted that the outermost radial portion of the tooth is narrower at its end which is at the large diameter of the conical gear. Such a tooth has heretofore been difficult to shave unless special shaving cutters were used having a hollow lead, or, for example, having a shape which was opposite to the shape desired to be formed on the gear. I-Ieretofore, it has been impossible to form a conical gear having crowned teeth with a standard cylindrical cutter.

FIG. 3a is a lead chart of the conical gear, crowned tooth shown in FIG. 3, such a chart being well known in the art and made by a lead checking machine. Line 3b-3b in FIG. 3 shows the path of the lead measuring probe when used to make the chart in FIG. 3a, and the line 312-322 is parallel to the axis of the conical gear. The arrow 30 of the chart shows the path of the probe coming onto the tooth while the arrow 3d shows the path of the probe leaving the tooth, all in accordance with the conventional lead ch'art making procedure. It will be seen that the path 3e of the lead measuring probe is curved to the plus side of the centerline, representing a crowned tooth. It will be noted that the paths of the probe along the two sides of the tooth are not exactly the same length because the sides of the tooth are not of the same length due to the fact they are helical conical gear teeth.

FIG. 3b shows the cross sectional shape of the tooth of FIG. 3, the view being taken generally along the line 3b-3b in FIG. 3.

FIG. 2, 2a, and 2b are generally similar to FIGS. 3, 3a and 3b, respectively, except FIGS. 2, 2a and 2b show a typical prior art tooth of the hollow lead type. In this chart the leads are hollow as shown by the lead paths curving to the minus side of the centerline. The centerline can be thought of as representing a straight lead conical gear. This hollow lead type of tooth does not have the desirable center of tooth" contact with a mating straight lead conical gear, for example, and this tooth results in frequent breakage and damage to the gear teeth, due to the end loading on the tooth.

FIG. 8 shows a portion of a gear cutting machine including a stationary frame 1 having a stationary head 2 on which a conventional, cylindrical, shaving cutter C is driven by a motor M in the head in either direction of rotation. The machine also includes a table 4 which reciprocates in an axial direction relative to the cutter axis, as indicated by the arrow 5. The table is also mounted about a transverse axis 6 so that the table may be rocked about its axis 6, as indicated by curvilinear arrow 8, in accordance with conventional, tooth crowning practice.

A conical gear holding attachment A is provided for the table 4 of the machine, the attachment having a frame 9 which is pivoted by means of a horizontal hinge 10 at one end so that its other end may be vertically positioned and fixed in any one of a number of vertical positions by the bolts 11 which extend through arcuate slots 12 in the bracket 13 that is fixed to the machine table 4. With this adjustment, the angle of tilt of the attachment can be varied to make gears of different sizes, and angles. The conical gear G to be shaved is freely rotatably mounted by the holding means 14 and 15 rotatably mounted on the spindles 16 and 17, respectively, of the attachment.

FIGS. 4, 5, 6 and 7 indicate the relative position of the conical gear G to the shaving cutter C during a cutting pass and then when the gear begins another cutting pass in the opposite direction.

Generally, during this shaving operation, the conical gear is positioned so that its pitch line 20 (FIG. 5) is parallel to the pitch line 22 of the shaving cutter, at the point of adjacency of the gear and cutter, that is in the cutting zone. In other words, the pitch lines of the gear and cutter are in parallelism during the shaving operation, except for the very slight rocking of the gear axis GA to effect crowning of the gear tooth.

This rocking movement has been shown very much exaggerated in FIG. 4, the rocking of the gear axis GA being in the direction of the arrows 23. In this position, the gear is offset to one side of the cutter, but still in mesh therewith, as when beginning a cutting pass under the cutter. After the gear has passed the centerline of the cutter, which centerline position is shown in FIG. 5, the axis of the gear is rocked in the other direction, namely in the direction of arrows 32 in FIG. 6. In FIG. 6 this rocking is again shown as very much exaggerated for the purpose of illustrating the invention.

Referring again to FIG. 4, when the gear G commences its cutting pass, that is its movement in the direction of the arrow 25, relative to the stationary cutter, it will be noted that the gear and cutter are in mesh and rotating in the direction of the curvilinear arrows 26 and 27, respectively. As the gear moves towards the position shown in FIG. 5, its axis is rocked progressively and minutely until it is parallel to the stationary axis 30 of the tooth shaving cutter C.

The gear continues movement in the direction of the arrow 31 until it reaches the end of the cutting pass shown in FIG. 6, and during this movement to the FIG. 6 position, the axis is rocked in the opposite direction, namely as shown by the arrows 32. It will again be noted that the gear and cutter are still meshed when the end of the cutting pass has been reached in FIG. 6.

Before the next cutting pass is made by the gear moving in the opposite direction as indicated by the arrow 34 in FIG. 7, the direction of rotation of the gear and cutter have been reversed and they are then rotating in the direction of the curvilinear arrows 35 and 36, respectively. The gear then moves in the direction of the arrow 34 and its axis is rocked minutely in the direction of arrows 38 due to the rocking of table 4, and relative to the cutter until the other end of the cutting pass has been reached which has been shown in FIG. 4.

Thus, a series of cutting passes is used to shave the gear, and the degree of rocking of the gear axis is adjustable and determines the amount of crown on the gear. With the present invention, that is to say with the gear pitch line arranged in parallelism to the cutter pitch line, except for the rocking of the gear, a gear having either a straight or crowned tooth can be shaved with the conventional, cylindrical shaving cutter.

Resume The present invention provides a method of and machine for shaving a conical spur or helical gear, and using a straight cylindrical cutter which eliminates the need for costly cutters of the prior art type. These prior art cutters, which were of opposite form to that desired to be imparted to the gear, required considerable time to design and manufacture.

By means of the present invention, the angle to which the conical gear is adjusted in the machine can be changed to provide for the shaving of a wide range of gears, that is gears having different numbers of teeth and angle, all being shaved with the same cutter.

Furthermore, the amount of crown can be easily varied to produce the desired degree of crown defined by the design strength of requirements, all with the use of a conventional cylindrical shaving cutter.

Thus, a conical gear either of the spur, helical, or the like type can be formed by means of the present invention and provided with the desirable crowned tooth configuration. Such a gear tooth overcomes the problems of tooth end loads and eliminates the majority of the trouble resulting from minute misalignments in normal assembly.

The gear teeth made in accordance with the present invention reduce the noise-level of the gears while in operation and increase durability of the gears because of the elimination of the end bearing concentration. The improved gears have improved and varying contact areas and they are produced by the present invention at an economical cost in respect to both tooling and production since the conventional cylindrical cutters are easier and require less time to design and manufacture, are more versatile, and a fewer number of cutters are needed to produce a variety of gears.

I claim:

1. A method of shaving a conical gear with a standard rotating cylindrical cutter comprising,

rotatably supporting the gear with its axis positioned at an angle with respect to the axis of said cutter so that the gear and cutter are in shaving mesh, providing a cutting pass between said gear and cutter in an axial direction of said cutter and simultaneously and progressively rocking and thereby crowning the gear during the cutting pass.

2. A method of shaving a conical gear with a standard cylindrical rotating cutter'comprising,

rotatably supporting the gear with its axis positioned at an angle with respect to the axis of said cutter so that the pitch line of the gear located adjacent the cutter lies along and adjacent the pitch line of the cylindrical cutter and the cutter and gear are in shaving mesh,

providing a cutting pass between said gear and cutter in one axial direction of said cutter and simultaneously and progressively rocking the axis of said gear in one direction in respect to said cutter axis to thereby effect a crowning on said gear,

providing a cutting pass between said gear and cutter in an opposite axial direction of said cutter while said gear and cutter rotation are reversed and simultaneously and progressively rocking the axis of said gear in the opposite direction to effect a crowning of said gear.

3. A method of shaving a conical gear with a standard rotatably driven cylindrical cutter comprising,

rotatably supporting the gear with its axis positioned at an angle with respect to the axis of said cutter so that during a cutting pass of the gear, the cutter and gear are in shaving mesh, and providing a cutting pass between said cutter and gear, rocking the gear relative to the cutter during the cutting pass to provide crowning of the gear teeth,

maintaining the gear pitch line which is adjacent the cutter in parallelism with the pitch line of the cutter except for crowning rocking of the gear relative to the cutter.

4. In combination with a machine for shaving a conical gear, said machine having a rotatably driven, stationary and cylindrical cutter, a table mounted for reciprocation beneath and in the direction of the axis of said cutter, said table also being mounted for rocking movement about a horizontal axis transverse in respect to the direction of said reciprocation; of a conical gear holding attachment mounted rigidly on said table for reciprocation and rocking therewith, said attachment including a frame arranged at an inclined angle to said table; said frame including holding means for freely rotatably mounting said conical gear in mesh with said cutter, whereby the pitch lines of the meshing teeth of said cutter and gear are in substantial parallelism.

5. The combination set forth in claim 4 including means for adjusting the angle of said holding means relative to said table to accommodate gears of different sizes and angles.

6. The combination set forth in claim 4 further characterized in that said frame is pivotably mounted at one end and said other end is vertically swingable to any one of a number of adjustably fixed positions.

7. The combination set forth in claim 5 further characterized in that said frame is pivotably mounted at one end and said other end is vertically swingable to any one of a number of adjustably fixed positions. 

1. A method of shaving a conical gear with a standard rotating cylindRical cutter comprising, rotatably supporting the gear with its axis positioned at an angle with respect to the axis of said cutter so that the gear and cutter are in shaving mesh, providing a cutting pass between said gear and cutter in an axial direction of said cutter and simultaneously and progressively rocking and thereby crowning the gear during the cutting pass.
 2. A method of shaving a conical gear with a standard cylindrical rotating cutter comprising, rotatably supporting the gear with its axis positioned at an angle with respect to the axis of said cutter so that the pitch line of the gear located adjacent the cutter lies along and adjacent the pitch line of the cylindrical cutter and the cutter and gear are in shaving mesh, providing a cutting pass between said gear and cutter in one axial direction of said cutter and simultaneously and progressively rocking the axis of said gear in one direction in respect to said cutter axis to thereby effect a crowning on said gear, providing a cutting pass between said gear and cutter in an opposite axial direction of said cutter while said gear and cutter rotation are reversed and simultaneously and progressively rocking the axis of said gear in the opposite direction to effect a crowning of said gear.
 3. A method of shaving a conical gear with a standard rotatably driven cylindrical cutter comprising, rotatably supporting the gear with its axis positioned at an angle with respect to the axis of said cutter so that during a cutting pass of the gear, the cutter and gear are in shaving mesh, and providing a cutting pass between said cutter and gear, rocking the gear relative to the cutter during the cutting pass to provide crowning of the gear teeth, maintaining the gear pitch line which is adjacent the cutter in parallelism with the pitch line of the cutter except for crowning rocking of the gear relative to the cutter.
 4. In combination with a machine for shaving a conical gear, said machine having a rotatably driven, stationary and cylindrical cutter, a table mounted for reciprocation beneath and in the direction of the axis of said cutter, said table also being mounted for rocking movement about a horizontal axis transverse in respect to the direction of said reciprocation; of a conical gear holding attachment mounted rigidly on said table for reciprocation and rocking therewith, said attachment including a frame arranged at an inclined angle to said table; said frame including holding means for freely rotatably mounting said conical gear in mesh with said cutter, whereby the pitch lines of the meshing teeth of said cutter and gear are in substantial parallelism.
 5. The combination set forth in claim 4 including means for adjusting the angle of said holding means relative to said table to accommodate gears of different sizes and angles.
 6. The combination set forth in claim 4 further characterized in that said frame is pivotably mounted at one end and said other end is vertically swingable to any one of a number of adjustably fixed positions.
 7. The combination set forth in claim 5 further characterized in that said frame is pivotably mounted at one end and said other end is vertically swingable to any one of a number of adjustably fixed positions. 